More lethal (8)
I believe the answer is:
deadlier
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">more lethal</span>' is the definition.<br/ ><span class="explanation-format__explanation">('deadly' can be a synonym of 'lethal')</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for deadlier that I've seen before include "more like the female, it's said" , "More lethal or fatal" .)